1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device and a method of fabricating an LCD device, and more particularly, to a transflective-type LCD device and a method of fabricating a transflective-type LCD device.
2. Discussion of the Related Art
Currently, many different types of flat display devices are being developed, such as LCD devices, field emission display (FED) devices, electroluminescent display (ELD) devices, and plasma display panel (PDP) devices. Among these various types of flat display devices, the LCD devices are commonly used due to their thin profile, light weight, and low power consumption.
The LCD devices may be classified into one of two different types: a transmitting-type LCD device and a reflective-type LCD device, according to use of a light source. The transmitting-type LCD device uses a backlight device, wherein the transmitting-type LCD device can display images in relatively low light surroundings by controlling a light transmittance according to alignment of liquid crystal molecules. However, the transmitting-type LCD device requires high power consumption. On the other hand, the reflective-type LCD device makes use of ambient light, thereby requiring a relatively small amount of power consumption. However, the reflective-type LCD device cannot display images in relatively low light surroundings, such as when there is cloudy or unclear weather. Accordingly, the reflective-type LCD is commonly used for electronic equipment, such as watches or calculators, that require low power consumption, and the transmitting-type LCD device is commonly used for large-sized notebook computers requiring production of high quality images.
In order to overcome the problems of the transmitting- and reflective-type LCD devices, a transflective-type (reflective-transmitting) LCD device has been developed. The transflective-type LCD device can operate as the reflective- or transmitting-type LCD device depending on the surrounding light conditions. For example, when large amounts of ambient light is available, the transflective-type LCD device may be enabled to function as the reflective-type LCD device, wherein the ambient light incident through an upper substrate is reflected onto a reflective electrode. Conversely, in relatively low light surroundings, the transflective-type LCD device may be enabled to function as the transmitting-type LCD device using the backlight device, wherein the light emitted from the backlight device is incident to liquid crystal material through an opening part of the reflective electrode.
FIGS. 1A to 1F are cross sectional views of a method of fabricating a transflective-type LCD device according to the related art. In FIG. 1A, a low-resistance conductive metal layer is deposited onto a transparent substrate 11 made of glass or quartz by a sputtering method, and a gate line (not shown) and a gate electrode 12 are formed by a photolithographic process using a first mask. Accordingly, the gate lines are formed along one direction at fixed intervals, wherein the gate electrode 12 diverges from each of the gate lines. Forming the gate line and gate electrodes includes coating a photoresist material, which is sensitive to ultraviolet light, onto the substrate, exposing and developing the photoresist material using a mask to form a photoresist pattern, etching material layers using the photoresist pattern, and stripping the photoresist pattern away.
Next, silicon nitride SiNx or silicon oxide SiOx is deposited along an entire surface of the substrate 11 including the gate electrode 12 by a PECVD method to form a gate insulating layer 13. Then, a first amorphous silicon layer and a second amorphous silicon layer doped with n-type impurities are sequentially deposited onto an entire surface of the substrate 11 including the gate insulating layer 13, and patterned by a photolithographic process using a second mask, thereby forming the semiconductor layer 14. The second amorphous silicon layer doped with the n-type impurities is formed to provide an ohmic contact with subsequently-formed source/drain electrodes, and the island-shaped semiconductor layer 14 is formed on the gate insulating layer 13 above the gate electrode 12.
In FIG. 1B, a low-resistance metal layer is deposited along an entire surface of the substrate 11 including the semiconductor layer 14, and patterned by a photolithographic process using a third mask to form a data line (not shown) and the source/drain electrodes 15a/15b. Accordingly, the data line crosses the gate line to define a pixel region, and the source/drain electrodes 15a/15b are formed at both sides of the semiconductor layer 14. Thus, a thin film transistor includes the gate electrode 12, the semiconductor layer 14, and the source/drain electrodes 15a/15b. Although not shown, a portion of the ohmic contact layer is removed directly above a channel region of the semiconductor layer 14.
In FIG. 1C, an organic insulating layer having photosensitive light characteristics is formed along an entire surface of the substrate 11 including the thin film transistor by a spin-coating method, thereby forming a passivation layer 16 having a predetermined thickness. Then, a photoacryl resin is deposited onto an entire surface of the substrate 11 including the passivation layer 16, and a plurality of photoacryl resin patterns are formed at fixed intervals by a photolithographic process using a fourth mask. As a result, hemispheric projection patterns 90 are formed by a reflow of the photoacryl resin patterns. Next, a predetermined portion of the passivation layer 16 is removed by a photolithographic process using a fifth mask to form a contact hole 18 exposing the drain electrode 15b. 
In FIG. 1D, a transparent conductive material, such as ITO (indium-tin-oxide), is deposited on the passivation layer 16 including the plurality of projection patterns 90, and patterned by a photolithographic process using a sixth mask, thereby forming a transmitting (transparent) electrode 17 contacting the drain electrode 15b. 
In FIG. 1E, an insulating interlayer 24 is deposited along an entire surface of the substrate 11 including the pixel electrode 17, and a portion of the insulating interlayer 24 corresponding to the contact hole 18 is removed by a photolithographic process using a seventh mask. Accordingly, some portion of the drain electrode 15b or the transmitting electrode 17 is exposed by the contact hole 18.
Subsequently, a metal layer having a high reflexibility, such as aluminum Al, copper Cu, or silver Ag, is formed along an entire surface of the substrate 11 including the insulating interlayer 24, and patterned by a photolithographic process using an eighth mask, thereby forming the reflective electrode 19. At this time, the reflective electrode 19 contacts the drain electrode 15b or the transmitting electrode 17 through the contact hole 18, wherein the reflective electrode 19 is formed within the reflective part of a unit pixel region. For example, the reflective electrode 19 is formed of the high reflexibility metal in the reflective part of the unit pixel region, and the transmitting electrode 17 is formed of the transparent conductive material in the transmitting part, thereby completing a thin film transistor (TFT) substrate 11 having both transmitting and reflective functions.
In FIG. 1F, the TFT substrate 11 is disposed opposite to a color filter substrate 33 having a color filter layer by a sealant, and includes spacers disposed between the TFT and color filter substrates 11 and 33 to maintain a cell gap. Then, a liquid crystal material is injected through an inlet into the cell gap between the TFT and color filter substrates 11 and 33 to form the liquid crystal layer 40. Next, the inlet for injection of the liquid crystal material is sealed, thereby completing the LCD device.
According to the related art, the TFT substrate 11 includes an amorphous silicon semiconductor layer formed using a photolithographic process using eight separate masks. For example, the processes for forming the gate line (not shown), the semiconductor layer 14, the data line (not shown), the contact hole 18 of the passivation layer 16, the transmitting electrode 17, the contact hole of the insulating interlayer 24, the projection pattern 90, and the reflective electrode 19 each requires its own individual mask and mask step.
FIGS. 2A to 2G are cross sectional views of another method of fabricating a transflective-type LCD device according to the related art. In FIG. 2A, a buffer layer 152 of silicon oxide is formed along an entire surface of a transparent substrate 111 made of glass or quartz. Then, an amorphous silicon layer is formed on the buffer layer 152, and a laser beam is irradiated onto the amorphous silicon layer, thereby the crystallizing the amorphous silicon layer into a polysilicon layer 144. The process of crystallizing the amorphous silicon into the polysilicon may be performed using various different methods. Among these various different methods, a Field Enhanced Metal Induced Crystallization (FEMIC) technique using catalytic metal is commonly used, which has advantageous characteristics including rapid crystallization speed, low cost, and suitability for large-sized glass substrates.
In FIG. 2B, the crystallized polysilicon layer 144 is patterned by a photolithographic process using a first mask, thereby forming an activated semiconductor layer 154.
In FIG. 2C, an inorganic insulating layer, such as silicon nitride SiNx or silicon oxide SiOx, is formed along an entire surface of the substrate 111 including the semiconductor layer 154 to form a gate insulating layer 113. Then, a metal layer of aluminum Al or aluminum alloy A1Nd is formed on the gate insulating layer 113, and patterned by a photolithographic process using a second mask to form a gate electrode 112. Then, n-type impurity ions are implanted into the semiconductor layer 154 using the gate electrode 112 as a mask, thereby forming source/drain regions 115a and 115b. In addition, a channel layer 114 is formed between the source region 115a and the drain region 115b. Although not shown, a gate line is simultaneously formed with the gate electrode 112.
In FIG. 2D, an inorganic insulating layer of SiNx or SiOx is formed along an entire surface of the substrate 111 including the gate electrode 112 to form a first insulating interlayer 123. Then, the first insulating interlayer 123 and the gate insulating layer 113 are selectively removed by a photolithographic process using a third mask to form a first contact hole 181 exposing the source/drain regions 115a and 115b. 
Next, a metal layer of aluminum Al or aluminum alloy AlNd is formed on the first insulating interlayer 123 to bury the first contact hole 181, and patterned by a photolithographic process using a fourth mask. Accordingly, source/drain electrodes 115c and 115d are formed and connected to the source/drain regions 115a and 115b. Thus, a polysilicon TFT (poly-TFT) comprising the gate electrode, the polysilicon semiconductor layer, and the source/drain electrodes may be formed.
In FIG. 2E, an inorganic insulating material of silicon nitride or an organic insulating material of BCB is deposited along an entire surface of the substrate 111 including the poly-TFT, thereby forming a passivation layer 116. Then, photoacryl resin having photosensitive characteristics is deposited along an entire surface of the substrate 111 including the passivaiton layer 116, and patterned by a photolithographic process using a fifth mask. Accordingly, a plurality of projection patterns 190 are formed at fixed intervals by a reflow process. The projection patterns 190 are formed in a predetermined part including a reflective part, whereby a reflective electrode is formed along a surface of the substrate including the plurality of projection patterns 190. Accordingly, the reflective electrode includes the plurality of projection patterns 190 to obtain a wide viewing angle by scattering the ambient light. Then, a predetermined portion of the passivation layer 116 is removed by a photolithographic process using a sixth mask to expose the drain electrode 115b, thereby forming a second contact hole 191.
In FIG. 2F, a transparent conductive material, such as ITO (indium-tin-oxide), is deposited along an entire surface of the substrate 111 including the plurality of projection patterns 190, and patterned by a photolithographic process using a seventh mask, thereby forming a transmitting electrode 117 in the pixel region to contact the drain electrode 115b. 
In FIG. 2G, a second insulating interlayer 124 is deposited along an entire surface of the substrate 111 including the transmitting electrode 117, and the second insulating interlayer 124 corresponding to the second contact hole 191 is removed by a photolithographic process using an eighth mask. Accordingly, some portion of the drain electrode 115b or the transmitting electrode 117 is exposed by the second contact hole 191. Subsequently, a metal layer of high reflexibility material, such as aluminum Al, copper Cu, or silver Ag, is formed along an entire surface of the substrate 111 including the second insulating interlayer 124, and patterned by a photolithographic process using a ninth mask, thereby forming the reflective electrode 119. Accordingly, the reflective electrode 119 is connected to some portion of the drain electrode 115b or the transmitting electrode 117 through the second contact hole 119, and the reflective electrode 119 is formed in the reflective part of the unit pixel region. For example, the reflective electrode 119 using the high reflexibility metal is formed in the reflective part of the unit pixel region, and the transmitting electrode 117 using the transparent conductive material is formed in the transmitting part, thereby fabricating a TFT substrate 111 that operates having both transmitting and reflective functions.
Accordingly, the TFT substrate 111 of the transflective-type LCD device including the poly-TFT requires photolithographic processes using nine separate masks. For example, the processes for forming the semiconductor layer 154, the gate line (not shown), the first contact hole 181, the data line (not shown), the second contact hole 191 of the passivation layer 116, the projection pattern 190, the transmitting electrode 117, the second contact hole 191 of the second insulating interlayer 124, and the reflective electrode 119.
However, according to the related art, the transflective-type LCD device and the method of fabricating the transflective-type LCD device have disadvantages, such as the number of photolithographic processes increases, fabrication costs and errors of the fabrication process increases, and productivity decreases.